1. Field of the Invention
The present invention relates to a cooling device, a semiconductor package on which the cooling device is mounted and a computer which includes this semiconductor package, and more particularly to a preferred cooling device which dissipates heat from either of the semiconductor package and a substrate on which the semiconductor package is mounted.
2. Description of the Related Art
With the recent progress of the integration of electronic circuits, in substrates including semi-conductor packages in which semiconductor chips containing electronic circuits are packaged, heat generated per unit area tends to increase. Some packaging substrates such as a printed circuit board, on which a variety of semiconductor packages and electronic parts are mounted, often include semiconductor packages which generate more heat than ordinary semiconductor packages. When these substrates are mounted on electronic devices in high concentration, in order to have the semiconductor packages work stably it is necessary to maintain the temperatures of the semiconductor package or the substrate at predetermined values and thus it is necessary to dissipate heat from the surface of the substrate or an electronic device effectively.
As a method for dissipating heat from these semiconductor packages, substrates and electronic devices including the semiconductor packages or substrates, Japanese Patent Unexamined Publication No. 2-130894, for example, has disclosed a method for blowing air to a plurality of substrates by means of a large size rotation fan which produces air flow in a computer.
Japanese Patent Unexamined Publication Nos. 2-83958 and 2-196454 have disclosed a cooling method for directly providing a circuit substrate with a miniature size rotation fan.
Moreover, Japanese Patent Unexamined Publication No. 62-149158 has disclosed a method for directly providing a circuit substrate with a reciprocating type fan employing a piezo-vibrator instead of the miniature size rotation fan.
According to the method for blowing air to a plurality of substrates by means of a large size rotation fan in the prior art described above, it is difficult to feed air uniformly to all of the substrates and if a semiconductor package having a high heat generation density is mixed into the substrate, it is difficult to cool the respective elements uniformly. A further problem is that the fan occupies a large area in the computer.
The method in which a miniature size fan or a reciprocating type fan unit employing a piezo-vibrator is directly mounted on a substrate is effective for the substrate on which the semiconductor packages having high heat generation density are mixedly mounted.
However, with the miniature size rotation fan, the efficiency of the fan tends to decrease and additionally, since space for air to be blown to the semiconductor package is needed, a wide space in a direction perpendicular to the substrate is required. With the reciprocating type fan employing the piezo-vibrator, it is necessary to locate the fan away from the surface of the substrate to blow air to the surface of the substrate. On the other hand, if the height of the fan from the substrate is reduced so that the fan edges operate as if they sweep the surface of the substrate, the fan scans only a part of the substrate surface, and thereby the cooling efficiency is not satisfactory.